Polyacetal resins (also referred to as polyoxymethylene resins, and abbreviated as POM resins) have balanced mechanical properties as well as excellent friction/abrasion resistance properties, chemical resistance, thermal resistance, electrical properties, and the like, and thus are widely used in the fields of automobiles, electric/electronic products, and the like.
However, required properties in these fields are increasingly demanding. As an example, further improvements are desired in not only general physical properties but also sliding properties. The aforementioned sliding properties mean friction/abrasion properties against inorganic-filler compounding materials. As an example, inorganic-filler compounding materials in which inorganic fillers such as glass fiber, glass flake, talc, and mica are blended with acrylonitrile-butadiene-styrene copolymer synthetic resin (ABS resin), polycarbonate (PC)/ABS resin, polybutylene terephthalate (PBT)/ABS resin are increasingly popular for use in chassis of CD-ROMs in response to demanding requirements for cost/weight reduction.
Conventionally, gear components and lever components usually slide against metal bosses caulked on sheet metal chassis, and thus friction/abrasion properties against metal materials have been important. However, when those members such as bosses are integrally molded with chassis using the aforementioned resin materials, the slidability against resin bosses and resin guides becomes more important.
Sliding against the aforementioned resin chassis materials requires much better friction/abrasion properties as compared with those required for sliding against conventional metal materials due to intrinsically poor friction/abrasion properties of ABS resin and the like as a counterpart member, adverse effects of a compounded inorganic filler on surface roughness, and the like. Therefore, improvements have been required.
Usually, a fluororesin or a polyolefin-based resin is added to a polyacetal resin in order to improve sliding properties. Alternatively, lubricating oils such as fatty acid, fatty acid ester, silicone oil, and various mineral oils are added.
Although addition of a fluororesin or a polyolefin-based resin may improve sliding properties to some extent, these resins have poor compatibility with polyacetal resins, resulting in unsatisfactory sliding properties under high surface pressure and poor abrasion resistance when sliding against an inorganic-filler compounding material.
In order to solve the aforementioned problems, a polyacetal resin composition is proposed, the polyacetal resin composition being obtained by melt kneading (A) a polyacetal resin, (B) a modified olefin-based polymer modified with at least one selected from the group consisting of unsaturated carboxylic acid and acid anhydrides thereof and derivatives thereof, and (C) an alkylene glycol-based polymer having a number average molecular weight of 400-500,000 and having a primary amino group or a secondary amino group, in which the (B) component is included in an amount of 1 to 100 parts by weight relative to 100 parts by weight of the (A) component, and the (C) component is included in an amount of 0.1 to 100% by weight relative to the (B) component (for example, see Patent Document 1).
Further, a polyacetal resin composition is proposed, the polyacetal resin composition being obtained by: blending (A) 100 parts by weight of a polyacetal resin with (B) 0.5 to 100 parts by weight of a modified olefin-based polymer in which (B-1) an olefin-based polymer is modified with at least one selected from the group consisting of (B-2) unsaturated carboxylic acid and acid anhydrides thereof and derivatives thereof, (C) 0.01 to 10 parts by weight of an alkylene glycol-based polymer having a number average molecular weight of 400 to 500,000 and having a primary amino group or a secondary amino group, and (D) 0.1 to 20 parts by weight of an inorganic filler; and performing melt kneading (for example, see Patent Document 2).
Moreover, a polyacetal resin composition is proposed, the polyacetal resin composition being obtained by blending (A) 100 parts by weight of a polyacetal resin with (B) 0.5 to 100 parts by weight of a modified olefin-based polymer in which (B-1) an olefin-based polymer is modified with at least one selected from the group consisting of (B-2) unsaturated carboxylic acid and acid anhydrides thereof and derivatives thereof, and (C) 0.1 to 20 parts by weight of an inorganic filler; and performing melt kneading (for example, see Patent Document 3).
Patent Document 1: PCT International Publication No. WO96/34054
Patent Document 2: Japanese Unexamined Patent Application, Publication No. H10-130457
Patent Document 3: Japanese Unexamined Patent Application, Publication No. H10-130458